Seen these on e-Bay and they look like an interesting alternative for attaching things like lights and other gadgets to handlebars. I'm putting together an alternative mount for my GPS and I think I'm gonna use a couple of these instead of a velcro attachment as these look like they will attach really tightly and still be easily removable without tools.

Does anyone have any experience of them?

They work fine, provided you wrap a bit of inner tube round the bar first to stop any slippage.
I used one to bodge an old phone mount to some bars.

Received the ties today, and they are excellent. Just using one of these ties my Etrex GPS is now really firmly mounted onto my stem with my DIY bracket, and can be removed to change bikes within a few seconds – much superior to the Garmin official bracket.